2020-MAY-15 Network Upgrade Specification

Date: 2020-04-26

Version: 0.4

Summary

When the median time past [1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1589544000 (May 15th, 2020, 12:00PM UTC),
Bitcoin Cash will execute an upgrade of the network consensus rules according to this specification.
Starting from the next block these consensus rules changes will take effect:

Bitcoin Cash’s SigOps counting and limiting system is replaced with a new system, referred to as SigChecks.

A new opcode called OP_REVERSEBYTES has been added to the script system.

OP_REVERSEBYTES

Infrastructure Funding Plan

The purpose of the Infrastructure Funding Plan (IFP) is to provide funding to development projects working on common Bitcoin Cash infrastructure.
If activated, it enforces that 5% of the block reward is spent to one of a set of specified addresses.
Activation is triggered via BIP 9 version bits signalling prior to the May 15 upgrade.

Automatic Replay Protection

The purpose of Automatic Replay Protection is to serve as a full node version-deprecation mechanism. It is intended to cause
full validating nodes which do not upgrade, to automatically separate themselves from the main network after the next
upgrade on 15 May 2020. Nodes which implement the next upgrade will remove this automatic replay protection, and thus all regular
wallets can continue using the default ForkID with no change to follow the main upgraded chain.

When the median time past [1] of the most recent 11 blocks (MTP-11) is less than UNIX timestamp 1605441600 (Nov 2020 upgrade)
Bitcoin Cash full nodes MUST enforce the following rule:

forkid [2] to be equal to 0.

When the median time past [1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1605441600
(Nov 2020 upgrade) Bitcoin Cash full nodes implementing the May 2020 consensus rules SHOULD enforce the following change:

Update forkid [2] to be equal to 0xFFXXXX, where XXXX is some arbitrary hex value.
ForkIDs beginning with 0xFF will be reserved for future protocol upgrades.

This particular consensus rule MUST NOT be implemented by Bitcoin Cash wallet software. Wallets that follow the upgrade
should not have to change anything.

References

[1] Median Time Past is described in bitcoin.it wiki.
It is guaranteed by consensus rules to be monotonically increasing.